Die Verwendung virtueller 3D-Modelle und quantitativer Untersuchungsmethoden in der Archäoseismologie am Beispiel der Archäologischen Zone Köln

Die Archäoseismologie hat sich in den letzten Dekaden zu einem eigenen, multidisziplinären Wissenschaftszweig entwickelt. Durch die Weiterentwicklung von quantitativen Methoden wurden der Archäoseismologie zudem neue Werkzeuge zur Verfügung gestellt. In der vorgestellten Studie wurde der multidisziplinäre Ansatz weiterentwickelt und neue quantitative Methoden, insbesondere die Schadensauswertung basierend auf virtuellen 3D Modellen und numerische Modellierungen zur Plausibilitätsabschätzung von Schadensszenarien, wurden auf das Beispiel der Archäologischen Zone Köln angewendet. Während der Einrichtung dieses unterirdischen Museumskomplexes in der historischen Altstadt von Köln, wurden bei Grabungen Reste der römischen und mittelalterlichen Bebauung freigelegt. In einem 150 x 200 m großen Areal zeigen die neu ergrabenen Gebäudereste und Gebäude die schon in der 1950er Jahren freigelegt wurden, strukturelle Gebäudeschäden. Hinzen und Schütte (2003) haben Teile der Schäden an den in den 1950er Jahren freigelegten Fundamenten des römischen Statthalterpalastes (Praetorium) untersucht und einen möglichen seismogenen Ursprung der Schäden vermutet. Durch die derzeitigen Grabungen ergibt sich die Möglichkeit die Erdbebenhypothese und mögliche alternative Schadensursachen mit Hilfe von neuen quantitativen Methoden in einem multidisziplinären Ansatz zu untersuchen. Auf Grundlage der Kartierung des Gebäudebestandes mit einem Phasenlaserscanner konnten virtuelle 3D-Modelle der archäologischen Befunde erstellt werden. Anhand dieser Modelle wurden die Gebäudeschäden identifiziert, klassifiziert, lokalisiert und quantifiziert. Die Ergebnisse der Schadensanalyse wurden in einer Datenbank zusammengefasst. Die strukturellen Gebäudeschäden wurden in dieser Studie mit simulierten Schadenszenarien verglichen. Der Großteil der Schäden deutet auf Bewegungen im Baugrund der Archäologischen Zone hin, die nicht notwendiger Weise durch Erschütterungen während eines Erdbebens verursacht wurden. Neben der Kartierung der Gebäudeschäden wurden der lokale Baugrund und die Topographie des Arbeitsgebietes untersucht. Diese Untersuchungen zeigen, dass die Gebäude in der Archäologischen Zone auf einem sehr komplexen Untergrund, nahe der Kante eines Hanges zu einem ehemaligen Seitenarm des Rheins errichtet wurden. Diese Situation wurde vereinfacht und unter Verwendung vorhandener und neu erhobener Daten auf ein geotechnisches Untergrundmodell des Arbeitsgebietes übertragen. Das resultierende Finite-Element-Modell wurde zur Plausibilitätsabschätzung von Schadensszenarien genutzt. Neben der statischen Hangstabilität wurde das Verhalten des Hanges unter seismischer Belastung sowie der Einfluss von Niederschlagswasser auf den Baugrund untersucht. Für die Berechnungen des Verhaltens unter dynamischer Belastung wurden synthetische Seismogramme für 16 Erdbebenszenarien genutzt, die standortspezifisch auf Grundlage eines seismotektonischen Modells der Region berechnet wurden. Die Wirkung von Niederschlagsereignissen wurde mit einem hydrologischen Modell des Untergrundes untersucht. Grundlage ist das Bemessungsregenereignis für die Stadt Köln mit einer Wiederkehrzeit von 100 Jahren. Die Ergebnisse der Modellrechnungen unter statischer und dynamischer Belastung haben gezeigt, dass die Hangstabilität sowohl im statischen Lastfall als auch unter Erdbebenbelastung gegeben ist. Die hydrologischen Modellrechnungen haben gezeigt, dass Niederschlagswasser in Bereiche mit kohäsionslosen Sanden versickern und dort Untergrunderosion verursachen kann. Die Ergebnisse der Schadensanalyse und der numerischen Modellierungen sowie die archäologische Situation im Arbeitsgebiet zeigen, das Erosionsprozesse im Untergrund eine plausible Erklärung für die beobachteten Schäden sind

Comparative study of the growth of sputtered aluminum oxide films on organic and inorganic substrates

We present a comparative study of the growth of the technologically highly relevant gate dielectric and encapsulation material aluminum oxide in inorganic and also organic heterostructures. Atomic force microscopy studies indicate strong similarities in the surface morphology of aluminum oxide films grown on these chemically different substrates. In addition, from X-ray reflectivity measurements we extract the roughness exponent \beta of aluminum oxide growth on both substrates. By renormalising the aluminum oxide roughness by the roughness of the underlying organic film we find good agreement with \beta as obtained from the aluminum oxide on silicon oxide (\beta = 0.38 \pm 0.02), suggesting a remarkable similarity of the aluminum oxide growth on the two substrates under the conditions employed

Strongly Enhanced Thermal Stability of Crystalline Organic Thin Films Induced by Aluminum Oxide Capping Layers

We show that the thermal stability of thin films of the organic semiconductor diindenoperylene (DIP) can be strongly enhanced by aluminum oxide capping layers. By thermal desorption spectroscopy and in-situ X-ray diffraction we demonstrate that organic films do not only stay on the substrate, but even remain crystalline up to 460C, i.e. 270 deg. above their desorption point for uncapped films (190C). We argue that this strong enhancement of the thermal stability compared to uncapped and also metal-capped organic layers is related to the very weak diffusion of aluminum oxide and the structurally well-defined as-grown interfaces. We discuss possible mechanisms for the eventual breakdown at high temperatures.Comment: 5 pages, 4 figures, submitted to Adv. Mat., for further information see http://www.physchem.ox.ac.uk/~f

Pitfall of vertebral artery insonation: Bidirectional flow without subclavian artery pathology

SummaryBackgroundA bidirectional flow pattern within the intracranial segment of the vertebral artery (V4–VA) should be indicative of a proximal steno-occlusive disorder of the ipsilateral subclavian artery (SA). Here we present two patients revealing this ultrasound finding without evidence of a specific SA pathology.Methods/case reportsIn case 1 duplex sonography revealed a diameter of the left V2–VA of 3.3mm and 2.7mm on the right side. Normal flow signals were detected in the left V2–VA, a systolic flow deceleration was seen on the right side. Intracranially, a biphasic flow pattern was observed in the right V4–VA. The left V4–VA, the basilar artery and the brachial arteries (BrA) as well as the cuff-test were normal. Conventional angiography ruled out a SA or VA pathology. A bilateral fetal-type posterior cerebral artery (FT-PCA) was seen. CT angiography demonstrated a small diameter of the right intracranial V4–VA close to the basilar confluens.In case 2 VA diameter of the left and right V2–VA was 3.3 and 2.3mm, respectively. Flow signals, similar to case 1 were observed in the non-dominant V2–VA and V4–VA segment. The remaining vessels and the cuff-test were normal. MR angiography demonstrated a FT-PCA and an incomplete posterior inferior cerebellar artery (PICA)-ending VA on the right side.ConclusionsA bidirectional flow in V4–VA can not prove a subclavian steal phenomenon. A normal triphasic flow signal of the brachial artery excludes a relevant proximal obstruction of the SA. Also, diameter measurements of the VA are mandatory.It seems that physiological variants of the vertebrobasilar circulation like a VA hypoplasia, PICA-ending VA or FT-PCA might also cause the above type of VA flow pattern

Left ventricular apical thrombus after systemic thrombolysis with recombinant tissue plasminogen activator in a patient with acute ischemic stroke

BACKGROUND: Thrombolysis with recombinant tissue plasminogen activator (rtPA) is an established treatment in acute stroke. To prevent rethrombosis after rtPA therapy, secondary anticoagulation with heparin is commonly performed. However, the recommended time-point and extent of heparin treatment vary and are not well investigated. CASE PRESENTATION: We report a 61-year-old man who developed an acute global aphasia and right-sided hemiparesis. Cranial CT was normal and systemic thrombolytic therapy with tPA was started 120 minutes after symptom onset. Low-dose subcutaneous heparin treatment was initiated 24 hours later. Transthoracic echocardiography (TTE) 12 hours after admission showed slightly reduced left ventricular ejection fraction (LVEF) but was otherwise normal. 48 hours later the patient suddenly deteriorated with clinical signs of dyspnea and tachycardia. TTE revelead a large left ventricular apical thrombus as well as a reduction of LVEF to 20 %. Serial further TTE investigations demonstrated a complete resolution of the thrombus and normalisation of LVEF within two days. CONCLUSION: Our case demonstrates an intracardiac thrombus formation following rtPA treatment of acute stroke, probably caused by secondary hypercoagulability. Rethrombosis or new thrombus formation might be an underestimated complication of rtPA therapy and potentially explain cases of secondary stroke progression

Effects of probiotics and antibiotics on the intestinal homeostasis in a computer controlled model of the large intestine

Background: Antibiotic associated diarrhea and Clostridium difficile infection are frequent complications of broad spectrum antibiotic therapy. Probiotic bacteria are used as therapeutic and preventive agents in these disorders, but the exact functional mechanisms and the mode of action are poorly understood. The effects of clindamycin and the probiotic mixture VSL#3 (containing the 8 bacterial strains Streptococcus thermophilus, Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei and Lactobacillus delbrueckii subsp. Bulgaricus) consecutively or in combination were investigated and compared to controls without therapy using a standardized human fecal microbiota in a computer-controlled in vitro model of large intestine. Microbial metabolites (short chain fatty acids, lactate, branched chain fatty acids, and ammonia) and the intestinal microbiota were analyzed. Results: Compared to controls and combination therapy, short chain fatty acids and lactate, but also ammonia and branched chain fatty acids, were increased under probiotic therapy. The metabolic pattern under combined therapy with antibiotics and probiotics had the most beneficial and consistent effect on intestinal metabolic profiles. The intestinal microbiota showed a decrease in several indigenous bacterial groups under antibiotic therapy, there was no significant recovery of these groups when the antibiotic therapy was followed by administration of probiotics. Simultaneous application of anti- and probiotics had a stabilizing effect on the intestinal microbiota with increased bifidobacteria and lactobacilli. Conclusions: Administration of VSL#3 parallel with the clindamycin therapy had a beneficial and stabilizing effect on the intestinal metabolic homeostasis by decreasing toxic metabolites and protecting the endogenic microbiota from destruction. Probiotics could be a reasonable strategy in prevention of antibiotic associated disturbances of the intestinal homeostasis and disorders. © 2012 Rehman et al; licensee BioMed Central Lt

Pattern of Activated Pathways and Quality of Collateral Status in Patients with Symptomatic Internal Carotid Artery Occlusion

Background: Internal carotid artery occlusion (ICAO) is an important risk factor for stroke. Cerebral hemodynamics in patients with ICAO depends on the individual capacity to activate sufficient collateral pathways. Therefore, the assessment of intracranial collaterals is essential for the acute and long-term management of these patients and accurate estimation of further stroke risk. Methods: Acute stroke patients with unilateral ICAO were prospectively enrolled. We assessed the following collaterals by transcranial color-coded sonography (TCCS): the anterior and posterior communicating artery (ACoA, PCoA), the ophthalmic artery (OA), and leptomeningeal collaterals of the posterior cerebral artery (LMC). We subdivided the flow pattern of the Doppler spectrum in the middle cerebral artery (MCA) into 3 categories: (1) good, (2) moderate, and (3) bad according to the hemodynamic effects on the ipsilateral MCA flow. Finally, we compared the individual TCCS results with the stroke pattern detected on CT or MRI scan. Results: One hundred thirteen patients (age 66 +/- 12 years; female 24) were included. The collateral status was good, moderate, and bad in 59 (52%), 37 (33%), and 17 (15%) patients, respectively. The ACoA collateral was most frequently activated (81%), followed by the OA (63%), the PCoA (53%), and the LMC (22%). The quality of the collateral status was determined by the type (p = 0.0003) but not by the number (p = 0.19) of activated collateral pathways. Good collateral function was highly associated with primary collaterals (ACoA > PCoA). Best parameter for a good collateral status was an antegrade flow in the OA, indicating a high blood supply via the communicating arteries. Conclusions: TCCS allows the assessment of intracranial collaterals and their hemodynamic capacity. Prevalence of collateral sufficiency in ICAO seems to be higher than previously reported. ACoA cross flow is essential for the optimal hemodynamic compensation of ICAO. Antegrade OA flow indicates good collateral status